I think we all can agree that the material flowing from the south tower has a orange-yellow appearance.

This indicates a temperature of 980C - 1050C leaning on the heavy side as it looks more yellow than orange.

This is due to two laws of physics

"Emissivity—This is a dimensionless constant, the ratio of the energy radiated by a material to the energy radiated by a black body at the same temperature. This is the total energy across the emission spectrum. Emissivity is a number less than or equal to 1."

"Planck’s Law gives the spectral radiance of electromagnetic radiation of a black body. This is a function of frequency (or, equivalently, wavelength) and temperature. This law embodies the concept that the radiated spectrum as a function of frequency at a given temperature is the same shape for all radiating materials. The only factor affecting the radiated spectrum that depends on the nature of the material is emissivity, a constant, independent of frequency."

Some claim that its possible for the material flowing from the south tower to be aluminium, they claim the aluminium is heated to 980c thus giving it a orange yellow colour.

Aluminium melts at 660C at which temperature is looks silvery

The problem with concluding that the liquid flowing from the tower’s 82nd floor could have been aluminum is that the liquid in the tower was not confined in a container so that more heat could be applied to raise the temperature of the liquid above its melting point. Instead, as soon as the metal liquefied it flowed away from the heat source under the force of gravity. Therefore, the color of the liquid flowing from the 82nd floor was at approximately the melting point of the metal. And therefore, it was molten iron.

Here is a video example of aluminium being heated in a container to 980c or 1800 F...

As you can see the aluminium cools rapidly to a silvery colour, as metals are a great conductor of heat.

The molten material flowing from the south tower even remains orange yellow during its whole descent.

Ironically for debunkers NIST knows this and agrees that the molten material is not pure liquid aluminium, and have hypothesised a different scenario to make the aluminium orange yellow...

"11. Why do some photographs show a yellow stream of molten metal pouring down the side of WTC2 that NIST claims was aluminum from the crashed plane although aluminum burns with a white glow?NIST reported (NCSTAR 1-5A) that just before 9:52 a.m., a bright spot appeared at the top of a window on the 80th floor of WTC 2, four windows removed from the east edge on the north face, followed by the flow of a glowing liquid. This flow lasted approximately four seconds before subsiding. Many such liquid flows were observed from near this location in the seven minutes leading up to the collapse of this tower. There is no evidence of similar molten liquid pouring out from another location in WTC 2 or from anywhere within WTC 1.Photographs, and NIST simulations of the aircraft impact, show large piles of debris in the 80th and 81st floors of WTC 2 near the site where the glowing liquid eventually appeared. Much of this debris came from the aircraft itself and from the office furnishings that the aircraft pushed forward as it tunneled to this far end of the building. Large fires developed on these piles shortly after the aircraft impact and continued to burn in the area until the tower collapsed.NIST concluded that the source of the molten material was aluminum alloys from the aircraft, since these are known to melt between 475 degrees Celsius and 640 degrees Celsius (depending on the particular alloy), well below the expected temperatures (about 1,000 degrees Celsius) in the vicinity of the fires. Aluminum is not expected to ignite at normal fire temperatures and there is no visual indication that the material flowing from the tower was burning.Pure liquid aluminum would be expected to appear silvery. However, the molten metal was very likely mixed with large amounts of hot, partially burned, solid organic materials (e.g., furniture, carpets, partitions and computers) which can display an orange glow, much like logs burning in a fireplace. The apparent color also would have been affected by slag formation on the surface."

http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htmHowever as Dr. Jones demonstrated by experiment that organic material floats on the liquid aluminum and burns up (oxidizes). Further, the liquid aluminum in this experiment was never heated to the point where it no longer appeared silvery.This experiment gave the expected result. Organic material would not change the color vs temperature behavior of aluminum.The conclusion of this analysis is inescapable. The liquid metal was molten iron...

If any debunkers can show how to make aluminium orange yellow while getting it to flow from a building. Then officially this will be debunked.

Its not to hard to find aluminium it can be readily bought in the form of soda cans.